1. Field of the Invention
The present invention relates to a disk cartridge accommodating an information recording/reproducing disk and a disk drive apparatus to record or reproduce information on or from the disk. More particularly, the present invention relates to a disk cartridge and a disk drive apparatus having an improved identifying device to identify the disk type.
2. Description of the Related Art
A present design for a recording medium for multimedia such as audio and video includes a cartridge which rotatably accommodates a recording/reproducing medium such as an optical disk or an optical magnetic disk so that the disk can be used in a disk drive apparatus. The development of multimedia requires a larger capacity of a disk cartridge, and as a result a variety of disk cartridges with an improved recording density have been developed. For example, in the case of a digital versatile disk-random access memory (DVD-RAM), there are a variety of disk cartridges having different recording densities. These varieties include a normal one-sided disk on which information can be recorded on only one surface; a double-sided disk on which information can be recorded on both surfaces; a one-sided double recording layer disk having a double recording layer on one surface so that information can be recorded on each layer; a double-sided double recording layer disk having a double recording layer on both surfaces; and a one-sided disk having a narrower track pitch than the normal one-sided disk.
A recording and reproducing method of a disk drive apparatus changes depending on the recording density. In other words, a disk drive apparatus uses a different method when recording and reproducing information to and from a disk depending on the structure of a track pitch or a recording layer type (a single layer or a double layer). Accordingly, a structure for identifying the type of disk cartridge loaded to the disk drive apparatus is required.
FIG. 1 discloses a known structure for identifying the type of disk, as disclosed in Japanese Patent Publication No. hei 11-120733. Referring to FIG. 1, an identification magnet 5 to indicate a large capacity is installed on a disk cartridge 1 rotatably accommodating a disk 2 in a case 3. A disk drive apparatus 6 is provided with a magnetism sensor 7 to sense the magnet 5. When the disk cartridge 1 is loaded into the disk drive apparatus 6, the magnetism sensor 7 senses a magnetic force of the identification magnet 5, and determines that the disk cartridge 1 has a large capacity and transmits the determined result to a controller (not shown) of the disk drive apparatus 6 so that control suitable for the type of the disk cartridge 1 is performed. On the other hand, the identification magnet 5 is not installed on a disk cartridge having a small capacity. Thus, no magnetic force is sensed by the magnetism sensor 7 when the disk cartridge of a low capacity is loaded into the disk drive apparatus 6, thus it is determined that the currently loaded disk cartridge has a small capacity.
Since the known method identifies the type of disk cartridge 1 based on an on/off state of the magnetism sensor 7 depending on the existence/non-existence of the identification magnet 5, only two types of disks cartridges 1, for example, a large capacity and a small capacity, can be identified. Accordingly, to identify various types of disk cartridges 1 as described above with this known structure, it would be necessary to change the number of identification magnets 5 depending on the type of disk cartridge 1, install as many magnetism sensors 7 as the maximum number of identification magnets 5, and determine the type of disk cartridge 1 based on how many times the magnetism sensor 7 is turned on. Alternately, it would be necessary to install a identification magnet 5 having a different magnetic force depending on the type of disk cartridge 1, and to construct the magnetism sensor 7 with a circuit to accurately identify the strength of the magnetic force instead of a simple on/off structure.
However, increasing the number of identification magnets 5 and magnetism sensors 7 makes it difficult to realize a small and light disk drive apparatus, increases the manufacturing cost and reduces productivity. Furthermore, a structure that identifies the type of disk cartridge based on the strength of the magnetic force requires construction of an accurate circuit. Still further, when the magnetic force of the magnet is degraded, the type of disk cartridge may be erroneously identified. Therefore, a disk cartridge and a disk drive apparatus which have a simple structure allowing various types of disk cartridges to be identified are desired.